**Core Concept**
Drug-induced extrapyramidal syndromes (EPS) are movement disorders caused by dopamine receptor blockade, especially with first-generation antipsychotics. These syndromes result from impaired dopaminergic modulation in the basal ganglia, leading to acute motor disturbances.

**Why the Correct Answer is Right**
Dystonia is the most common early manifestation of drug-induced EPS, typically occurring within hours to days of starting antipsychotic therapy. It presents as sustained muscle contractions causing abnormal postures, especially in the neck, face, or limbs. This occurs due to acute dopamine D2 receptor blockade in the nigrostriatal pathway, disrupting basal ganglia output. Dystonia is often reversible upon discontinuation or dose reduction of the offending agent.

**Why Each Wrong Option is Incorrect**
Option B: Chorea is a movement disorder characterized by involuntary, dance-like movements, typically associated with Huntington’s disease or neuroleptic malignant syndrome, not commonly induced by antipsychotics.
Option C: Tardive dyskinesia is a chronic, often irreversible movement disorder that develops after prolonged use of antipsychotics, not the most common early EPS.
Option D: Hemiballismus is a rare, severe movement disorder caused by lesions in the internal capsule or basal ganglia, not a drug-induced condition.

**Clinical Pearl / High-Yield Fact**
Dystonia is the most frequent and earliest EPS seen with antipsychotics—especially in young patients or those on high-dose therapy—and is a key warning sign of neuroleptic sensitivity. Early recognition allows prompt intervention to prevent progression.

✓ Correct Answer: A. Dystonia